i want to build now the transform
[x' y' 1] = A*[X Y 1];
i have figured out that i would need to use repmat, but i can't seem to get to the real syntax without loops.
what's the most efficient way to do it?

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This is a programming question about MATLAB, and not a signal processing question. It should be migrated to a programming site on SE. If not, it should be closed here.
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Dilip SarwateDec 1 '12 at 21:53

Your last question as of now reads "... i can't seem to get to the real syntax without loops. what's the most efficient way to do it?" In what sense is this a signal processing question?
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Dilip SarwateDec 2 '12 at 3:24

thank for the answer ,i can share my whole code if that helps. let's a assume i have a 256X256 grayscale picture (imageB) i want to map into a bigger picture (imageA). so when i use the above code what i'll get will be X=256X256 and so will be Y=256X256. so the code for that will need to different than what you wrote, correct?
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GiladDec 1 '12 at 21:34

@Androidy, if you want to map images you should also add interpolation and use inverse transform. You should really take a look at how Matlab does it. Check out dsp.stackexchange.com/questions/4804/…
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AndreyDec 1 '12 at 21:47

my problem is not the image processing knowledge but more of a Matlab syntax, should i post this in StackOverFlow? i'm going to use bilinear interpolation, but before that i need to apply the inverse transform.
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GiladDec 1 '12 at 21:56

@Androidy, sorry, but I don't understand your problem. Can you please describe it better, including a reproducible code/ example?
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AndreyDec 1 '12 at 22:00

i have added my full code. and some more explanations thanks.
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GiladDec 1 '12 at 22:19